At one point or another, HDCP has probably stumped all of us. HDCP problems can be difficult to identify and aren’t often the first thing you begin troubleshooting when your setup won’t work. Established in 2000 and adopted in 2004, HDCP is a protocol that is meant to protect copyrighted content from being redistributed illegally while still being able to view it in the privacy of your own home. By description, it sounds like a perfectly acceptable idea, but in practice, it might just be one of the worst things ever created. It causes headaches not only for consumers, but also for professionals with complicated AV setups. What this generally means for us is when a system is setup, no content makes it to the display and the display is black or shows an error message. These problems can be challenging to troubleshoot.
HDCP is a rather straightforward process. When you connect a source to a display there is an HDCP handshake where the two devices exchange some bits of data that are then calculated with an algorithm to see if the device on the other end checks out. If everything looks good, then signal passes. If there are any errors, no signal goes through. These bits of data are called “keys.” Every device has a public key and a private key (more on this later). HDCP can be found on DVI, HDMI, DisplayPort, and a few less popular protocols.
HDCP has a pile of problems. The first is that it is completely 100% breakable with not too much work if you know what you’re doing. In fact, Scott Crosby and others released a paper in 2001 pointing out the fact that if a user obtains 40 private/public key combinations, they can create a master key that works with all HDCP devices, thereby rendering the protocol completely useless; and there is no way to combat this breach other than updating firmware on every HDCP device, which is impossible. This was before HDCP was the standard. Crosby suggested several alternate algorithms that were much more secure than HDCP, but yet the industry adopted HDCP the following year. It wasn’t until several years later that someone publicly released a master key for the first time. On the whole, HDCP still thwarts some attempts to duplicate copyrighted material but at the cost of many more users struggling with setups that won’t work with no idea why not.
In 2008, HDCP 2.0 was released. Other than sharing the name of its predecessor, it was nothing like HDCP 1.0. However, it was also cracked very quickly and rendered useless. 2.1 quickly followed, also cracked, also useless. The next iteration, HDCP 2.2, is on its way right now. It will be the HDCP version that ships with most new 4K displays. But wait, 4K displays are already shipping and HDCP 2.2 isn’t out yet? The protocols are backwards compatible, right? Wrong. Since earlier versions of HDCP are ineffective, 2.2 cannot be backwards compatible and still “protect” copyrighted content. Fortunately, this will affect consumers much more quickly than the entertainment industry. This means that older devices which, run an earlier version of HDCP, won’t be compatible with new 4K displays. Our HDCP 2.2 headaches are just around the corner as more and more shows and events use flat screen displays and new devices that may create HDCP mismatches.
There are already several ways to not encounter HDCP problems on shows. The first and all-around easiest option is for all devices in a system to be HDCP compatible in the first place. As long as you are not mixing and matching 2.2 and an older version of HDCP, a system will be fine. Another easy way is to use a display protocol that doesn’t support HDCP, such as SDI. When these options don’t work, you may run into some problems with HDCP. For example, you may be using an older LED processor that doesn’t support HDCP or your setup may include international devices (HDCP is primarily a North American protocol). Professional-grade components such as a Lightware DVI/HDMI matrix have a feature that lets you disable HDCP with a simple checkbox. And if it comes down to it, there are some sketchy options like small HDMI devices that will strip HDCP signal. With either of these last two options, the transmitting device will see the destination as an HDCP-capable device but the outgoing signal will be HDCP free. It really only matters on the transmitting end that HDCP work. Display devices that support HDCP can take any signal whether or not it has HDCP.
HDCP 2.2 adds a whole new level of complication to the video world especially with more and more new 4K devices hitting the market. Hopefully, HDCP problems won’t become more frequent with these new complications on a protocol that is already quite terrible.